1. Field of the Invention
The present invention relates to a device for ultrasonic detection techniques for the inspection of weld defects in a fuel rod weldment.
2. Technical Background
In general, a fuel rod for use in a light water pressurized reactor is made by packing fuel pellets inside a fuel pipe, and the ends of the fuel pipe are fitted with end plugs and the end plugs are joined to the ends of the fuel pipe by means of joining techniques such as the tungsten inert gas (TIG) welding. Further, there is a (gas) seal opening disposed on one of the two end plugs for filling the fuel pipe interior with an inert gas under pressure. The gas seal opening is sealed off, by joining methods such as TIG welding, so as to maintain the interior of the fuel pipe at a certain inert gas pressure.
Conventionally, the joints of the fuel rod welded as described above have been inspected non-destructively by X-ray transmission. However, the X-ray method is being superseded by the ultrasonic inspection method which is more compact in apparatus design and easier to handle.
The ultrasonic inspection apparatuses which have been available to date are based on scanning the entire circumferential periphery of the weld by moving the detection probe linearly in the longitudinal direction while turning the fuel rod. When examining the weld by moving the detection probe in the longitudinal direction while rotating the fuel rod, there are no problems when the examination is being carried out at a rough scanning pitch or at low speeds. However, when it is desired to carry out inspection at a faster operating speed or at a finer scanning pitch, it was necessary to increase the rotational speed of the fuel rod, which lends to high loads on the rod and insufficient processing time for obtaining proper inspection results.